Mean Water Level Research Articles

Flood pulses drive the temporal dynamics of assemblages of aquatic insects (Heteroptera and Coleoptera) in a temperate floodplain

SummaryLowland riverine floodplains are among the most dynamic and heterogeneous of ecosystems, but many have been extensively modified. Their provision of important habitats provides a key motivation for restoring natural flow regimes (in terms of magnitude, frequency, duration, timing and rate of change of hydrological conditions). Despite general recognition that aquatic insects respond to changes in water availability, there is little agreement about the influence of flow regime components on community structure in floodplains.We analysed a 6‐year (2005 and 2007–2011) data set of aquatic insects (Heteroptera and Coleoptera) in a large Danubian floodplain characterised by pronounced hydrological variability. We hypothesised that abundance and assemblage structure would depend on flow regime components. In particular, we predicted that high‐flow events in the mainstream and concurrent high‐magnitude floods of prolonged duration would have a positive effect on diversity and abundance and that insect assemblages would differ between phases of hydrological connectivity. In addition, we assessed whether the survival of two threatened aquatic insects,Graphoderus bilineatusandBerosus geminus, depends on hydrological connectivity.Abundance and species richness of Heteroptera and Coleoptera increased during years with frequent extremely high flood pulses and prolonged flooding. Multivariate ordination showed subtle relationships between hydrological conditions, hydrological connectivity and insect assemblages with number of days in flood providing the best fit. Spring floods had a more pronounced effect on the assemblages than autumn floods. The time lag between flood occurrence and its apparent effect on aquatic insects was 17–31 days, reflecting insect life cycles.The abundance ofG. bilineatus(Coleoptera: Dytiscidae) was affected by mean water level during the month preceding sampling, whereas the abundance ofB. geminus(Coleoptera: Hydrophilidae) was related to the occurrence of prolonged high‐magnitude floods.The current water regime of the Danube River favours generalist species with high dispersal capacities and broad niches and food resources. Changes in flow management practices could remove the positive influence of floods on aquatic insect communities and lead to losses of threatened species that depend on these river–floodplain habitats. Our results contribute to the understanding necessary for appropriate evaluation and prioritisation of international floodplain conservation efforts.

Analyzing the Amur River water regime for the period preceding the catastrophic flood in 2013

The regime of rainfall floods in the Amur River basin in 1901–2011 (before the catastrophic flood in 2013) is analyzed using the data from the Khabarovsk hydrological station. Considered is the relationship between the annual maxima of floods and monthly mean water levels in September for that period. Revealed is the cyclicity of the Amur River water regime that has the form of the consecutive alternation of the groups of low- and high-water years for the period under consideration. This enables assessing qualitatively the trend in the water regime. Carried out is the comparative analysis of catastrophic water levels in the Amur River both during the summer low-water period in 2008 when the absolute minimum was registered at the flood wave peak, and during the flood in 2013.

Remediating Platforms by Raising Topsides

Technology Update The design of fixed offshore platforms requires a minimum clearance from the mean water level to the topsides structure. This clearance is generally referred to as an air gap. The air gap is determined such that under the maximum design conditions, the crest of the wave passing through the platform does not make contact with or inundate the topsides. Design codes such as API RP2A assess the air gap using the 1,000-year return period crest elevation combined with storm surge effects. Platform loads (shear and overturning moment) can increase by between 50% and 100% when the storm crest elevation exceeds the air gap and inundates the structure of the topsides. The consequences of a storm wave impact on a platform’s topsides can be catastrophic. This was graphically shown by the collapse or near destruction of a number of offshore structures in the US Gulf of Mexico (GOM) during hurricanes Ivan in 2004 and Katrina and Rita in 2005. Approximately 250 significant structures, including eight-leg drilling and production platforms in water depths of up to 450 ft, were destroyed by these storms collectively. Cleanup operations for the destroyed platforms remain ongoing. Costs for decommissioning a hurricane-destroyed platform are 10 times or greater the cost of decommissioning the same standing platform in a planned manner, excluding the value of lost or deferred oil and gas production. Given that the destroyed platforms were designed according to approved standards and guidelines, why did the structures collapse? Three primary reasons have been identified. The platforms were in poor condition (suffering from corrosion and historical damage) and thus had design resistances less than planned for in the original design. The maximum wave or waves experienced during these hurricanes were larger than assumed during the original design. Because wave loading on fixed offshore platforms varies with the square of the wave height, the actual loads experienced would be greater than those accounted for in the original design. And if the extreme wave crest exceeded the air gap, the design loads would increase exponentially and greatly exceed the original design case. The air gap for certain platforms was less than at the original time of installation, which resulted in unexpected topsides inundation. An Unacceptable Air Gap In view of the critical nature of the air gap in the design and long-term viability of an offshore platform, what are the circumstances under which the air gap distance would no longer be acceptable? Three specific cases should be considered. Actual design waves and storm surges are greater than those contemplated in the original design. The consequence factor used for the design of the platform has changed, thereby requiring the use of new and more onerous conditions (larger design waves). The platform air gap has decreased because of the offshore platform settling vertically relative to the mean sea level. Research conducted after the major hurricanes in 2004 and 2005 showed that the numerical storm wave hindcast models, which add updated information to original forecast models, underpredicted extreme wave heights for the central portion of the GOM, compared with data measured during these storms. The environmental criteria for the 100-year and 1,000-year return periods used for offshore platform design must be extrapolated from historical data recorded over much shorter time frames. Large variations in predicted values can arise from small errors made in fitting the historical data to complex statistical models. For example, the 100-year design wave in the GOM before these major storms was specified with a height of 72 ft. The updated 100-year design wave is now 91 ft, an increase of more than 25%. This would imply that the air gap selected for platforms designed to handle the smaller design wave will now be too small for the larger design wave condition.

Variations of the glacier mass balance and lake water storage in the Tarim Basin, northwest China, over the period of 2003–2009 estimated by the ICESat-GLAS data

Accurately estimating the changes in glacier mass balance and water storage in lakes and reservoirs is critical to studying the water cycle in the inland river basin in northwest China. We used high-resolution satellite images to analyze the changes in water surface area of lakes and reservoirs in Tarim Basin, and used the ICESat-GLAS altimeter data to estimate their water level changes and the glacier mass balance change, over the period 2003–2009. The results showed the average glacier thinning in the entire basin was at a rate of 0.34 ± 0.25 m w.e./year equivalent height of water, which means that the glacier mass balance occurred −6.8 ± 1.2 km3 water equivalent over the study period. However, the mean water level of nearby lakes decreased by 0.41 ± 0.2 m even with the influx of glacial melt water, indicating that the lake level declines were caused by the withdrawal of lake water for human activities.

Impact of Massanjore Dam on hydro-geomorphological modification of Mayurakshi River, Eastern India

Massanjore reservoir (area ~67 km2) located 84 km downstream from the most distant upstream source capacitates 620,000,000 m3 of water, and regulated flow characters are highly responsible for dam downstream alteration of hydrological, sedimentological and geomorphological characteristics of Mayurakshi River. In dam after condition, monsoon water level (mean water level during monsoon months) and pre-monsoon water level (mean water level during pre-monsoon months, i.e., March–May) have attenuated about 0.56 and 0.32 m, respectively. Maximum duration of high flow period during monsoon has reduced up to 16.5 %; coefficient of variation of diurnal fluctuation of water level during monsoon has increased from 31 to 47 %. Suspended sediment load in Mayurakshi River is reduced to 34 % in dam after period as recorded at Narayanpur gauge station. Average suspended sediment load has decreased even after Tilpara barrage construction from 4.960 to 4.350 mg/L. Average suspended sediment load is 7.875 mg/L in the sites of dam upstream course, and this average is only 4.46 mg/L in different sites of dam downstream course. Volume of discharge has decreased up to 11.3 % during monsoon time in dam after condition. Such reduction in discharge volume in turn has reduced about 24.6 % bed load-carrying capacity. As a result, huge deposition within channel invigorated channel bed aggradations (average 73.6 cm up to Saspara, site 14 at Fig. 1) in dam after condition. Narrowing of active channel, coarsening of channel bed materials, lowering of lateral stability, accelerating rise of braiding index, mixed response of the channel adjustment of the tributaries to local scale positive or negative base level change due to river bed aggradations and degradation, etc. signify the morphological alteration of dam downstream course. Open image in new window Fig. 1 Mayurakshi River basin indicating Massanjore Dam, Tilpara barrage and sample working sites

Numerical investigation of wave-induced flow in mound–channel wetland systems

Coastal wetlands are an important ecosystem in nearshore regions, but they are also significant in affecting the flow patterns within these areas. Wave-induced flow in wetlands has complex circulation characteristics because of the interaction between waves and plants, especially in discontinuous vegetation. Here, a numerical investigation is performed to analyze the wave-averaged flow in vegetated mound–channel systems. Different water levels, vegetated conditions, and mound configurations are studied with the COULWAVE (Cornell University Long and Intermediate Wave) Boussinesq model.Model simulations show rip currents in the mound–channel systems, whose strength varies with different mound separation distances. The relative influence of vegetation depends on both mound configuration and water level. Approximately a 15% change in significant wave height results as waves propagate over the vegetated mounds, while up to a 75% decrease in the mean shoreward flow speed through vegetation is observed. In addition, vegetation influences the spatial distribution of mean water level within the wetlands. Dimensional analysis shows that rip current strength and primary circulation size depend on mound spacing, water depth, wave height, and vegetation cover.

Accretion and Vegetation Community Change in the Wax Lake Delta Following the Historic 2011 Mississippi River Flood

Carle, M.V.; Sasser, C.E., and Roberts, H.H., 2015. Accretion and vegetation community change in the Wax Lake Delta following the historic 2011 Mississippi River flood.During the 2011 Mississippi River flood, discharge to the lower river exceeded that of the 1927 and 1937 floods and the lower river remained above flood stage for nearly 2 months. A combination of WorldView-2 and Land Satellite 5 Thematic Mapper (Landsat 5 TM) imagery was used to assess the impact of this flood event on the Wax Lake Delta, one of few areas where the river is building new land. Vegetation community change was mapped from 2010 to 2011 and related to elevation change using plant species elevation distributions calculated from light detection and ranging (LIDAR) data. Changes in the land area in the delta were also assessed by regressing land area against water level for a series of pre- and postflood Landsat 5 TM images. The results indicate a net growth of 6.5 km2 at mean water level and 4.90 km2 at mean sea level. Areal gains were greatest at high water levels, indicating substantial vertical accretion across the subaerial delta. At least 8.7 km2, or 31.8%, of the area studied converted to a higher-elevation species. The most change occurred at low elevations with conversion from fully submerged aquatic vegetation to Potamogeton nodosus and Nelumbo lutea. Conversion to lower-elevation species occurred across 3.4 km2, or 12.8% of the study area, while 55.5% remained unchanged. The results highlight the importance of infrequent, large flood events in the maintenance of river deltas and provide a reference for estimating the impact of proposed large-scale river diversions on the Mississippi River Delta.

Periodic seepage face formation and water pressure distribution along a vertical boundary of an aquifer

Detailed measurements of the piezometric head from sand flume experiments of an idealised coastal aquifer forced by a simple harmonic boundary condition across a vertical boundary are presented. The measurements focus on the pore pressures very close to the interface (x=0.01m) and throw light on the details of the boundary condition, particularly with respect to meniscus suction and seepage face formation during the falling tide. Between the low and the mean water level, the response is consistent with meniscus suction free models in terms of both the vertical mean head and oscillation amplitude profiles and is consistent with the observation that this area of the interface was generally within the seepage face. Above the mean water level, the influence of meniscus formation is significant with the mean pressure head being less than that predicted by capillary free theory and oscillation amplitudes decaying faster than predicted by suction free models. The reduced hydraulic conductivity in this area due to partial drainage of pores on the falling tide also causes a delay in the response to the rising tide. The combined influence of seepage face formation, meniscus suction and reduced hydraulic conductivity generate higher harmonics with amplitudes of up to 26% of the local main harmonic. To model the influence of seepage face formation and meniscus suction a numerical solution of the Richards' equation was developed and evaluated against the data. The model-data comparison shows a good agreement with the behaviour high above the water table sensitive to the choice of moisture retention parameters.

Re-evaluating luminescence burial doses and bleaching of fluvial deposits using Bayesian computational statistics

Abstract. The optically stimulated luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could potentially provide insights into sediment transport processes. However, comparison of bleaching between samples is complicated by sample-to-sample variation in aliquot size and luminescence sensitivity. Here we begin development of an age model to account for these effects. With measurement data from multi-grain aliquots, we use Bayesian computational statistics to estimate the burial dose and bleaching parameters of the single-grain dose distribution. We apply the model to 46 samples taken from fluvial sediment of Rhine branches in the Netherlands, and compare the results with environmental predictor variables (depositional environment, texture, sample depth, depth relative to mean water level, dose rate). Although obvious correlations with predictor variables are absent, there is some suggestion that the best-bleached samples are found close to the modern mean water level, and that the extent of bleaching has changed over the recent past. We hypothesise that sediment deposited near the transition of channel to overbank deposits receives the most sunlight exposure, due to local reworking after deposition. However, nearly all samples are inferred to have at least some well-bleached grains, suggesting that bleaching also occurs during fluvial transport.

Winter storm-induced hydrodynamics and morphological response of a shallow transgressive shoal complex: Northern Gulf of Mexico

Using extended deployments during seasons of low and high discharge from the Atchafalaya River, meteorological, hydrodynamic and bottom boundary layer parameters were monitored from Tiger and Trinity Shoal complex, off Louisiana coast, USA. During winter storms, the surface current speed measured at both shoals exceeded 0.5 m/s and the entire water column followed the prevailing wind direction. The current speed close to the bottom exceeded 0.3 m/s during high energy northerly winds. The mean water level in the shoal complex increased during southerly winds and decreased during northerly winds, such that the difference between wind set-up and set-down exceeded 0.7 m in Tiger Shoal and 0.6 m in Trinity Shoal during high energy frontal passages. The swell height was inversely correlated with mean water level, and increased during pre-frontal phase and decreased during post-frontal phase of winter storms. The sea (short waves) height responded quickly to wind direction and speed; and within a few hours after the wind shifted and blowing from the north, the sea height increased during both deployments. Bimodal wave frequency spectrum was observed during wind veering from southerly to northerly, when both sea and swell intensities were significant. The Tiger Shoal bed sediment texture transformed drastically, from mud to shell and shell hash assemblage, within a period of two weeks during the December 2008 deployment. Backscatter signal intensity from a Pulse Coherent Acoustic Doppler Profiler (PCADP) and its velocity estimates were used to determine the vertical extend and timing of mud resuspension and their eventual flushing out from the shoal environment, when exposed to high energy winter storm passages. The computed time frame for a total transformation of bottom sediment texture (from muddy bottom to shell and shell hash assemblage) was supported by the combined wave and bottom current induced shear stress at shoal bed. The bed samples collected from Tiger Shoal before and after the deployment in spring 2009 consisted of more than 80% shell and shell hash, which again confirmed a stable bottom as predicted from the PCADP data. However, the fine sand and mud dominated bed at Trinity Shoal was highly dynamic and experienced a few cm of ephemeral sediment deposition during the passage of each cold front, as revealed from the analysis of acoustic backscatter data from the PCADP. Suspended sediment concentration estimated from Optical Backscatterance Sensors (OBS) and PCADP were in good agreement during low river discharge events in December 2008; but significantly diverged during the spring 2009 deployment, when a high suspended sediment load was discharged into the shelf from the Atchafalaya River, and subsequently pushed farther offshore into the deployment sites by wind-induced strong currents during the passage of cold fronts.

Estudo numérico do escoamento em planícies de marés do canal Norte (estuário do rio Amazonas)

The analysis of the flow in tidal flats is essential to understanding the hydrodynamics of estuarine areas in the presence of macrotides. The river flow influence on tidal flats hydrodynamics is a rarely subject addressed in the literature. This numerical study was developed in the final stretch of the North Channel of the Amazon River, where a detail modeling was used to characterize the flow in the flooded regions due the tides. The tides control the water levels fluctuations, velocities and times of flooding and exposition inside the flats. The effect of river flow is only noticed in the upstream tidal flats, through changes in mean water levels, flats widths and velocities patterns, dampening the flood currents and amplifying the ebb’s. The flats were classified as flood-dominant systems, although the main channel has dominance in the ebb currents due to the presence of river flow. The numerical results indicated that tidal flats would be responsible for energy dissipation in the stretch under study and the generation of areas favoring the deposition of sediments near the coast.

Small Scale Field Experiment on Breaking Wave Pressure on Vertical Breakwaters

A small scale field experiment (SSFE) was performed on vertical breakwaters in the surf zone. The following are some of the findings. Wind seas may yield breaking wave pressure notwithstanding some large deepwater wave steepness, and small elevation of the wall above the mean water level. Caisson breakwaters can withstand some exceptionally high impulsive force peaks (even twice the weight in still water); whereas, with the same sea state and weight, a breakwater composed of layers of solid concrete blocks is destroyed.

ANewMethod forZoning ofCoastalBarriersbased onHydro-geomorphological andClimateCriteria

This paper presents a new methodology for the zoning of littoral sand barriers on the basis oftheir groundwater dynamic responses to the local mean water level (MWL) climate. The method is based onthe comparison of the characteristic scales of the horizontal drainage and recharge processes. Using theBoussinesq equation and basic hydro-geomorphological parameters, this methodology identifies the climaticevents that markedly affect the groundwater dynamics across the barrier, along with the location of the mostaffected cross sections. The application of the methodology to the Mar Menor sand barrier shows that asignificant number of cross sections can be particularly vulnerable to the effects of local storm events typicalof the Mediterranean coast during the spring and winter seasons. The location of the affected cross sections isanalyzed as a function of both the local MWL forcing and hydrogeological parameters. This case studyhighlights the possible use of the proposed methodology for land use planning and the environmentalmanagementof coastal sand bars.

Integrated modeling framework to quantify the coastal protection services supplied by vegetation

AbstractVegetation can protect communities by reducing nearshore wave height and altering sediment transport processes. However, quantitative approaches for evaluating the coastal protection services, or benefits, supplied by vegetation to people in a wide range of coastal environments are lacking. To begin to fill this knowledge gap, we propose an integrated modeling approach for quantifying how vegetation modifies nearshore processes—including the attenuation of wave height, mean and total water level—and reduces shoreline erosion during storms. We apply the model to idealized seagrass‐sand and mangrove‐mud cases, and illustrate its potential by quantifying how those habitats reduce water levels and sediment loss beyond what would be observed in the absence of vegetation. The integrated modeling approach provides an efficient way to quantify the coastal protection services supplied by vegetation and highlights specific research needs for improved representations of the ways in which vegetation modifies wave‐induced processes.

Characteristics of the changing seasonal water regime in Lake Dongting and their response to the change of river-lake water exchange in recent 30 years

The adjustment of river-lake water exchange will cause water regime of lake to change and threat the sustainable development of social economy and ecology. In this paper,based on daily observation data of water level and water discharge from 1981 to2012 at Chenglingji Station,Nanzui Station in Lake Dongting,Yichang Station and Luoshan Station in the main reaches of the Yangtze River,the characteristics of the changing water regime in Lake Dongting and their response to the changes of river-lake water exchange were analyzed by means of unit root test,analysis of variance and the comparison of stage-discharge curve. The results suggestted that the water regime in Lake Dongting showed periodic characteristics during 1981 to 2012. The period of 1981-2002 was viewed as relatively stable phase. Mean water level decreased 0. 43 m in 2003-2012. In the flood season,water level of Lake Dongting decreased 0. 60 m. In the retreating season,water level fell 1. 49 m. In the dry season,water level rose 0. 18 m. The change of water level was not significant in the rising season. The dry season may be early in consideration of 2. 03 m drop in October. The changes of hydrological regime were related to changes of river-lake water exchange: In the flood season,flow diversion at the three outlets reduced and the lake level dropped. In the retreating season,reduced flow diversion at the three outlets coupled with stepping up outflow intensified lake water withdrawal. In the dry season from January to March,outflow slowed down and the lake level rose.

Extreme structural response values from various methods of simulating wave kinematics

In offshore engineering, the main forces that are loaded onto ocean structures come from wind-generated random waves. The prediction of wave forces that are applied onto slender cylindrical members is usually based on the Morison's equation, in which the wave force at any section of a member is expressed directly in terms of wave kinematics. It is essential to be able to estimate sensible kinematics at all levels of a structure to determine accurate prediction of wave forces and corresponding responses of these structures in a random wave field. Linear random wave theory (LRWT) is the simplest and most often used to simulate water particle kinematics at different nodes of an offshore structure from a reference surface elevation record. However, water particle kinematics calculated from LRWT grossly overpredicts the kinematics above the mean water level (MWL). Methods have been introduced to overcome this problem of high kinematics above the MWL, which consists of using linear wave theory (such as Wheeler, vertical stretching, effective node elevation and effective water depth methods) to provide a more realistic representation of near-surface wave kinematics. This is promising as there is some evidence that the water particle kinematics from the Wheeler method are underestimated and that those from the vertical stretching method are somewhat exaggerated. In this paper, the comparisons of the probability distributions of extreme values from different methods of simulation wave kinematics are investigated by using conventional time simulation procedure.

IMAGE-BASED STUDY OF BREAKING AND BROKEN WAVE CHARACTERISTICS IN FRONT OF THE SEAWALL

This study aims to study the breaking and broken wave characteristics in front of the vertical seawall. Laboratory experiments were performed to represent such phenomena. A physical model of a vertical seawall installed on the mild slope was made in the wave flume. Image-based measuring technique was developed and applied to capture the wave characteristics as high-resolution data sets both in spatial and temporal domains. By analyzing the high-resolution data, behaviors of partial standing waves were successfully captured in front of the seawall. Comparisons of obtained data with and without seawall clearly showed the difference in cross-shore distributions of wave height, mean water level and skewness while no clear difference was observed in asymmetry. Obtained experimental data was then used to validate the applicability of Boussinesq wave model attached with existing breaking models. It was found that both viscosity-type and surface roller-type breaking models tended to overestimate the energy dissipation in front of the seawall.

EXPERIMENTAL STUDY ON GEOTEXTILE TUBE APPLICATIONS AS SUBMERGED BREAKWATERS FOR BEACH PROTECTION IN YUCATAN, MEXICO

The Yucatan coast, with a wide continental shelf and low sediment sources, is subject to a microtidal regime and low energy, short waves (Hs < 1 m, T=4-6s) with two main incident wave directions (from the E and NE) that generate a dominant westward longshore sediment transport. Approximately 60 of the 245 km extent of the Yucatan coastline have seen significant urban, industrial and touristic developments that have led to coastal erosion of 1 m/year over the last 10 years. In order to mitigate this trend, many structures (most of them emerged groins) have been constructed, but the majority of these efforts have been unsuccessful. From 2005 to 2007 geotextile tubes were empirically used as submerged breakwaters (GT-SBW) at several sites on the Yucatan coast, many of them placed between 10 and 30 m seaward from the shoreline. It was found that, in some cases, the beach was stabilized after placing the structure; but in other places the results were far from those expected. (Fig. 1). Considering the lack of knowledge in the design criteria and in the hydrodynamic performance of GT-SBW, this study analyses the results obtained through experimental tests using different model scales and geometries. The motivation for this study is to better understand the wave-structure interaction in terms of the effectiveness of the structure in minimizing the wave transmission coefficient (Kt). The main goal of this paper is to define optimal design criteria for the GT-SBW. The experimental tests were conducted in a wave flume (37x0.8x1.20 m) at the Coastal Engineering Laboratory of the Engineering Institute at UNAM, using two scales (1:5 and 1:10). The wave generation system is of a piston-type vertical paddle from HR Wallingford. Throughout statistical analysis of hindcast data, the mean wave regime was obtained in order to use representative data of the Yucatan coast. A total of 12 capacitance wave gauges were placed along the flume (before and after the structure) to record water surface elevations and to compute the transmission (Kt) and reflection (Kr) coefficients; Mansard and Funke’s (1980) separation method was used. During the experimental tests it was observed that the hydrodynamic behaviour of these structures is quite similar to that of low-crested breakwaters with very low permeability and that when the elevation of the breakwater crown is slightly below the mean water level, the waves break violently, thus dissipating wave energy. On the contrary, if the waves fail to break they are only steepened and the transmission coefficient can be even greater than one. From the data analysis it was found that the optimal freeboard should not exceed twice the design wave height. The experimental results and an empirical formula are shown in (Fig. 2).

EVALUATION AND DEVELOPMENT OF COASTAL PROTECTION MEASURES FOR SMALL ISLANDS IN THE WADDEN SEA

The Northfrisian Halligen are small undiked marsh islands and located in the German part of the UNESCO - World Natural Heritage Wadden Sea. The houses of the inhabitants are built on dwelling mounds and during storm events these mounds are the only places which are not inundated on the islands. With respect to climate change and related changes in mean and extreme water levels, new coastal protection measures and strategies have to be developed. At the Institute of Hydraulic Engineering and Water Resources Management (IWW) of the RWTH Aachen University different tools are used to evaluate and to develop new coastal protection measures and strategies for these islands. Within this project several new coastal protection measures and strategies for the Hallig islands have been developed and existing protection measures have been technically and economically evaluated. In addition, social accompanying measures were set-up to rise flood awareness and acceptance.

Clay mineralogical evidence of a bioclimatically-affected soil, Rouge River basin, South-Central Ontario, Canada

Holocene soils in drainage basins of South-Central Ontario, Canada, are generally Fluvisols (Entisols) in floodplains transitioning to Brunisols (Inceptisols), Luvisols (Alfisols) and Podzols (Spodosols) in older terraces and in the glaciated tableland. A single landslide sourced from the highest fluvial terrace in the Rouge basin, with a rubble drop of ~12m emplaced a lobe-shaped mass of reworked stream gravel, glaciolacustrine sediment and till, emplaced approximately 6m above mean water level at a height roughly equivalent to previously dated mid-Holocene terraces and soils. Clay mineralogy of the soil formed in this transported regolith produced the usual semi-detrital/pedogenic distribution of 1:1 (Si:Al=1:1), 2:1 and 2:1:1 clay minerals as well as primary minerals consisting of plagioclase feldspar, quartz, mica and calcite. Unexpectedly, the presence of moderate amounts of Ca-smectite in the Bk and Ck horizons, relative to a clay-mineral depleted parent material (Cuk), argues for a soil hydrological change affecting the wetting depth in the deposit. The presence of the uncommon ‘maidenhair fern’ (Adiantum pedantum) in the mass wasted deposit, a plant capable of high evapotranspiration, is interpreted as producing a bioclimatic disruption limiting soil water penetration to near root depth (wetting depth), thus producing a clay mineral anomaly.